This invention relates generally to the field of cataract surgery and more particularly to a handpiece tip for practicing the liquefracture technique of cataract removal.
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of the lens onto the retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and lens.
When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquifies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial lens.
Recently, a new cataract removal technique has been developed that involves the injection of hot (approximately 45° C. to 105° C.) water or saline to liquefy or gellate the hard lens nucleus, thereby making it possible to aspirate the liquefied lens from the eye. Aspiration is conducted concurrently with the injection of the heated solution and the injection of a relatively cool solution, thereby quickly cooling and removing the heated solution. This technique is more fully described in U.S. Pat. No. 5,616,120 (Andrew, et al.), the entire content of which is incorporated herein by reference. The apparatus disclosed in the publication, however, heats the solution separately from the surgical handpiece. Temperature control of the heated solution can be difficult because the fluid tubes feeding the handpiece typically are up to two meters long, and the heated solution can cool considerably as it travels down the length of the tube.
U.S. Pat. No. 5,885,243 (Capetan, et al.) discloses a handpiece having a separate pumping mechanism and resistive heating element. Such a structure adds unnecessary complexity to the handpiece.
U.S. Pat. No. 6,579,270 B2 (Sussman, et al.) discloses a surgical handpiece and tip having two coaxial tubes or channels mounted within a body. The first tube is used for aspiration and is smaller in diameter than the second tube so as to create an annular passage between the first and second tube. The annular passage communicates with a pumping chamber formed between two electrodes. The pumping chamber works by boiling a small volume of the surgical fluid. As the fluid boils, it expands rapidly, thereby propelling the liquid downstream of the pumping chamber out of the annular passage. The distal end of the annular gap is sealed by a nozzle at the distal ends of the first and second tube and a plurality of orifices or ports may be formed in the nozzle. As the expanding gas is propelled down the annular gap, the gas/liquid stream is forced out of the distal orifice in a controlled and directed manner. However, aspiration and irrigation flow patterns different that those described in this patent are sometimes desired, such as during cortical clean up or posterior capsule washing or lavage.
Therefore, a need continues to exist for a simple surgical handpiece and tip that can heat internally the solution used to perform the liquefracture technique.